Phencyclidine, a drug of public concern because of its illicit use and dangerous effects, has been the subject of little basic research. The proposed experiments will use validated methods to study effects of phencyclidine on emotional behavior in the nonhuman primate. The experiments proposed will study acute and chronic phencyclidine on aggression produced by antecedent and consequent stimulation and spontaneous aggression. Aggressive behavior will be elicited by the delivery of electric tail shock or by the termination of food delivery to the squirrel monkey subject. In other experiments aggressive behavior will produce delivery of food or avoidance of electric shock. Further experiments will study phencyclidine in a neutral environment in which stimuli are neither presented nor made contingent on any performance. Each of these experiments will study a complete dose response function of phencyclidine on both the acute and chronic regimens.